Soudan, Minnesota--Deep in a former iron mine in what is now a Minnesota
state park, scientists and government officials today (July 20) wielded
pickaxes to chip away, at least symbolically, at the mysteries surrounding
the subatomic particles known as neutrinos.
The miners-for-a-day in the Soudan Underground Mine State Park included Dr.
John O'Fallon of the U.S. Department of Energy, Professor Earl Peterson of
the University of Minnesota, Dr. Michael Witherell, director of DOE's Fermi
National Accelerator Laboratory, Professor Stanley Wojcicki of Stanford
University and Minnesota state and university officials. They took the first
steps in carving out a huge cavern, half a mile underground, that will be
home to a 5,000-ton steel particle detector. Physicists of the 200-member
MINOS (Main Injector Neutrino Oscillation Search) experiment will use the
detector to explore the question of neutrino mass.

Until recently, scientists believed that, unlike other fundamental particles
of matter, neutrinos possessed neither mass nor electric charge. However,
recent results from experiments in Japan, in Soudan itself and elsewhere
seem to point to a small mass for these elusive particles. Because they are
so numerous-each square meter of the atmosphere contains about 300
million-even a small mass for the neutrino would have big consequences for
our understanding of the nature and distribution of mass in the universe.

For the MINOS experiment, physicists at DOE's Fermilab, located 40 miles
west of Chicago, will use Fermilab's newly-completed Main Injector particle
accelerator to direct an intense beam of one type of neutrinos, called muon
neutrinos, to the underground Soudan detector, 450 miles away. Beginning in
early 2003, MINOS collaborators will use the detector to determine whether
some of the muon neutrinos in the beam have changed to another type, known
as tau neutrinos. Such a change, or oscillation, from one type to another,
would constitute clear evidence for neutrino mass and would allow physicists
to begin to calculate just how much mass the particles possess.

"This is an exciting opportunity in neutrino research," said Secretary of
Energy Bill Richardson, whose Energy Department funds over 90 percent of
federally sponsored particle physics research in the U.S. "New results are
yielding fresh insight into these fundamental particles, and in turn, into
the nature of matter and the universe. It is also an excellent example of
international scientific cooperation, with hundreds of scientists worldwide
participating, and funding partnerships that likewise span the globe."

The MINOS experiment differs from earlier neutrino-mass experiments because
it uses an accelerator-produced beam of neutrinos rather than
naturally-occurring neutrinos that stream to earth by the billions from
reactions in the sun and from cosmic ray interactions in the atmosphere.
Earlier experimenters detected fewer solar and cosmic-ray neutrinos than
they expected at detectors here on earth, leading them to conclude that one
type of neutrino had oscillated to another type and hence"disappeared"
from
detection. In contrast, the MINOS experiment is designed to detect not only
the disappearance of muon neutrinos, but also their appearance as neutrinos
of a different type, tau neutrinos.

^ÓThe study of fundamental properties of neutrinos is coming of age," said
University of Minnesota Professor of physics Earl Peterson, who manages the,
university's Soudan Laboratory."Solar and our own atmospheric experiments
have given us very remarkable data and opened up new possibilities for our
understanding of neutrinos. Now we need accelerator experiments to resolve
the possibilities and answer the questions they have raised."

Locating the detector half a mile below ground allows scientists to screen
out cosmic rays that would otherwise flood the particle detector with
unwanted signals. The changeover from iron mining to mining the secrets of
subatomic particles also provides economic stimulus to the northeastern
Minnesota area. The addition of construction jobs and operating personnel at
the Soudan site is estimated to contribute up to $15 million to the local
economy in the next few years. Iron ore for the $45 million detector's 486
steel plates will come from the Hibbing Taconite Company in nearby Hibbing,
Minnesota.

The MINOS experiment is a collaboration of some 200 scientists from DOE's
Argonne National Laboratory, the University of Athens (Greece), the
California Institute of Technology, the University of Chicago, JINR Dubna
(Russia), DOE's Fermilab, Harvard University, IHEP Beijing (Peoples Republic
of China), Indiana University, ITEP(Russia), Lebedev Institute (Russia), DOE
's Lawrence Livermore National Laboratory, University College London, the
University of Minnesota, Oxford University, the University of Pittsburgh,
IHEP Protvino (Russia), Rutherford Laboratory (England), the University of
Sussex (England), Texas A&M, the University of Texas at Austin, Tufts
University, and Western Washington University. Funding for the project comes
from DOE, the National Science Foundation, the State of Minnesota, and
science funding agencies abroad.

Fermilab is a Department of Energy National Laboratory dedicated to frontier research in the field of particle
physics. More than 90 percent of the funding for federally sponsored research in particle physics is provided by
DOE. Fermilab is operated by Universities Research Association, Inc. under contract with DOE.

For more information, call Fermilab's Public Affairs Office at (630) 840-3351.